Before TestingThe first step is to write a test plan. If you are working in the defense industry, a military test plan is usually a contract requirement. If not, you’ll still want one. If you don’t know enough to create one, ask your lab to do it, or to recommend an independent consultant who can help.

A good test plan includes:

A configuration, mode of operation, and monitoring method, which represents a worst case scenario from an EMC perspective

Special software, test fixtures, and supporting equipment may be needed to exercise the equipment under test

A description of hardware to be tested, including peripherals & I/O configurations

An indication of which external power and data I/O ports need to be tested for each test method

Required tests

A definition of failure criteria

How to monitor, recognize & report failures

Special needs: Software, power, cooling, etc.

Then, get pricing and scheduling from a leading 3rd party test lab, like MET Labs.

You’ll have to determine what the lab will supply versus what you will supply. You will need:

Equipment under test (EUT) & spares

Cables & connectors

Test fixture (for some programs)

Tool kit

EMI suppression supplies – ferrites, copper tape, etc.

The equipment’s design or compliance engineer or someone else familiar with the product to witness testing

In the Lab
Preliminary testing (pre-testing) is always a good idea. Shortened versions of each test method can be performed to identify failures. Design modifications can be made before final testing is scheduled. A radiated emissions pre-test, often referred to as a pre-scan, is the most common pre-test performed. Even if there is no plan to perform pre-testing for the other test methods, a radiated emissions pre-scan can identify failures and allow for design modifications, which will likely cause the equipment under test to perform better for the other test methods as well.

Then run the full program as specified in the test plan. If you pass the first time, congratulations! If not, don’t take it personally – it’s not unusual, especially with early-stage pre-compliance testing. And practically anything can be overcome.

If you fail a test, do some quick troubleshooting – you may be able to fix the problem right away. Do the easy things first:

Verify that the EUT is still working properly. This is particularly important with immunity tests that might cause damage.

Unplug external cables to see if it improves results. External cables, although not designed to do so, act as antennas to radiate emissions and receive RF interference.

Add ferrites to cables

Clean mating, conductive surfaces of paint and other materials.

Add an RF filter module at the power input to the equipment under test to limit RF emissions and protect from continuous conducted disturbances.

Add a MOVs or other transient limiting device at the power input to protect from transient disturbances.

To limit leakage, wrap the EUT in aluminum foil

For immunity, back off the test levels to determine the actual failure levels. If you are close, maybe a ferrite will fix things. If not, that’s good information to have – it will help you narrow the possible failure mechanisms.

Don’t be afraid to ask for suggestions. Test engineers at an experienced lab like MET will have seen hundreds if not thousands of products, and know many debug and quick-fix solutions.

MET Labs is a full-service EMC testing lab with multiple convenient locations. Contact us for a free quick-response quotation.

About MET Labs

MET Labs was established in 1959 and has become a global service leader for product approvals and regulatory certification of electrical products. In 1989, MET broke the UL monopoly for product safety testing and certification in the United States and is approved to certify products in over 200 UL standard categories. Today, MET is a global service leader for product approvals and regulatory certification of electrical products.

About Eurofins | MET Labs

MET Laboratories, Inc was established in 1959 and has become a global service leader for product approvals and regulatory certification of electrical products in Baltimore, MD. In 1989, MET broke the UL monopoly for product safety testing and certification in the United States and is approved to certify products in over 200 UL standard categories. MET Labs is a service leader and trusted provider of product testing and regulatory certification of electrical products for leading brands and companies in the United States, Europe and worldwide. In 2018, MET joined the Eurofins Scientific network and has become a key component in Eurofins’ product testing portfolio.

About the MET Mark

The MET Mark for product safety is accepted throughout the United States & Canada and indicates compliance to federal regulations for safe use in the workplace. 30 years ago, MET became the first OSHA-recognized NRTL (Nationally Recognized Testing Laboratory) in the United States. The NRTL mark is required under federal law for products used in workplaces in all 50 states. MET listed products are also sold in every major retail stores throughout the United States and Canada.